Various apparatus have been proposed for molding plastic caps having hold-down lugs or inclined tabs adapted to engage underneath a shoulder on a container, such as a vial, to hold the cap in a closed, sealed position on the container.
Before removing the finished cap from the molding apparatus, it is necessary that the tab forming components of the molding apparatus and the molded cap be reoriented relative to each other so that the cap tabs are free from any obstruction in the mold cavity, whereby the finished cap can be stripped from the mold cavity.
The reorientation of the finished cap and the tab forming components of the molding apparatus relative to each other is usually accomplished by either moving the tab forming components away from the tabs on the finished cap, or rotating the finished cap in a direction away from the tab forming components in the molding apparatus.
The molding apparatus of the present invention is constructed and arranged to rotate the finished cap relative to the tab forming components in the molding apparatus.
The apparatus of the present invention for molding plastic caps having inclined tabs and radially inwardly extending ribs comprises, essentially, a conventional injection molding core machine having a fixed platen assembly supporting a core and a movable platen assembly carrying a female mold having a cup-shaped cavity. Fixed and movable plate assemblies are positioned between the platen assemblies and the core extends upwardly through the movable and fixed plate assemblies to the female mold. A plurality of vertically extending blades are secured to one of the movable plate assemblies and are slidably mounted in axial grooves provided on the exterior surface of the core. The upper end portion of the blades are provided with recess having configurations corresponding to the inclined tabs and radially inwardly extending ribs on the plastic cap.
A linear drive member is mounted on one of the fixed plate assemblies and a ratchet sleeve is rotatably mounted on one of the movable plate assemblies and extends upwardly coaxially with the linear drive member. The ratchet sleeve is provided with a pair of axially extending, diametrically disposed offset slots which receive transverse pins connected to the linear drive member. The upper peripheral edge of the ratchet sleeve is provided with a plurality of circumferentially spaced teeth between which the plastic, forming the lower edge of the skirt of the cap, flows during the molding operation.
By this construction and arrangement, when the movable plate assembly carrying the ratchet sleeve moves upwardly, the pin connection between the linear drive member and the ratchet sleeve causes the ratchet sleeve to rotate, whereby the teeth on the end of the ratchet sleeve, engaging the lower edge of the cap skirt, causes the cap to rotate relative to the upper end portions of the blades to thereby move the cap tabs and ribs away from the tab and rib forming recesses prior to stripping the finished cap from the apparatus.